The term crank assembly is generally used to denote a connecting arrangement which is substantially in the form of a shaft assembly provided with offset crank portions, the purpose thereof being to transmit a force such as a drive force applied thereto at one location to a load connected thereto at another location. A distinction can be drawn between what can be referred to as horizontal crank assemblies and what can be referred to as vertical crank assemblies. If a power source such as a motor or engine is stationary with respect to the crank assembly and if a rotary movement is transmitted at the end from the output member of the power source to the crank assembly then such a design configuration is embraced by the term horizontal crank assembly, An example of this would be a crank assembly which is directly flange-mounted to the drive shaft of an electric motor. If in contrast the output of a drive assembly rotates about the horizontal, that is to say the longitudinal axis of a crank assembly, then that configuration is referred to by the designation vertical crank assembly. A drive arrangement of that kind would be for example a reciprocating piston engine whose piston rod or connecting rod moves around the crank assembly at one end in engagement with the offset crank portion of the crank assembly.
Crank assemblies are subjected to loadings resulting in flexural, torsional and oscillatory stresses. Oscillations for example progressively damage and destroy the structure of the material constituting the crank assembly and give rise to fatigue phenomena which ultimately can result in fracture of the crank assembly material. In order to obviate such fatigue fractures, crank assemblies can be provided with suitable devices, the purpose of which is to damp the oscillations involved. Suitable forms of mountings are increasingly used to counteract flexural phenomena while remedies are sought to counteract torsional phenomena in respect of the crank assemblies by virtue of a particular design configuration in respect of parts which trigger off inertia forces. In other respects crank assemblies are also characterized by the fact that the concentric portion of the crank assembly, more specifically the successively occurring drive input and drive output ends and the main bearing journals, and the eccentric portion of the crank assembly, more specifically the offset crank portions or crank throws and the crank journals, rotate at the same speed of rotation. When the concentric or the eccentric portion of the crank assembly is being driven, there is no possibility of causing the respective other portion of the crank assembly to rotate at a different speed. namely higher or lower.